A monitoring system for a segmental type display is disclosed in DE-OS No. 27 12 398. In the system disclosed therein, a comparator is provided for each line energizing one of the segments. A similar system, requiring a diode for each energizing lead is disclosed in U.S. Pat. No. 3,943,500, which is hereby incorporated by reference into this application. This type of monitoring circuit requires much extra equipment and is further useful only for displays in which a sufficient amount of current flows in the energizing leads (e.g. displays utilizing light-emitting diodes).
A system disclosed in DE-OS No. 24 06 093 illustrates a segmental display in which corresponding segment electrodes in the various display units are connected in series to form an electrode set. However, no monitoring system or method is disclosed in this reference.